Traditional orthogonal frequency division multiplexing(OFDM) transmitter is implemented by exploiting inverse fast Fourier transform(IFFT), up-sampling, and low pass shaping filter(LPSF) modules, which occupy a large ...Traditional orthogonal frequency division multiplexing(OFDM) transmitter is implemented by exploiting inverse fast Fourier transform(IFFT), up-sampling, and low pass shaping filter(LPSF) modules, which occupy a large number of hardware resources and severely lower down the operation speed. To address these limitations, we propose a novel OFDM transmitter architecture, by which the aforementioned modules can be discarded and replaced with some simple switches. In the proposed architecture, direct digital synthesis(DDS) method is employed to generate digital sub-carriers and to transform OFDM data from frequency domain to time domain. Through some sophisticated simplifications, the proposed architecture can avoid using multipliers and remarkably save hardware resources. Finally, comparative experiments are carried out on field programmable gate array(FPGA) platform which demonstrates that our DDS-based architecture saves more than half of the hardware resources and doubles the achievable maximum frequency compared with traditional structure.展开更多
This paper proposed an optimized fast handoff scheme for real time applications in next generation IP based CDMA wireless networks. The idea is to utilize optimized IP multicasting handoff (based on PIM SM), which is ...This paper proposed an optimized fast handoff scheme for real time applications in next generation IP based CDMA wireless networks. The idea is to utilize optimized IP multicasting handoff (based on PIM SM), which is triggered by CDMA layer 2 functionality. An IP based cellular network model with WCDMA FDD air interface and IP based packet traffic is adopted. No special network entities and signaling for handoff are added in our network model. The simulation results show that low delay and low packet lost rate can be obtained.展开更多
正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)调制因其高效的频带利用率和良好的抗多径能力广泛用于合作与非合作通信系统中。合作通信场景下,通常接收机可以利用已知帧结构实现OFDM信号的检测。但在非合作场景下,...正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)调制因其高效的频带利用率和良好的抗多径能力广泛用于合作与非合作通信系统中。合作通信场景下,通常接收机可以利用已知帧结构实现OFDM信号的检测。但在非合作场景下,接收机没有足够的先验信息,导致帧检测难度加大。针对这一问题,提出了一种适合于非合作通信场景的OFDM数据帧的检测算法。所提算法利用快速小波变换将含噪OFDM信号的功率包络进行小波分解与重构,对重构得到的功率包络进行差分运算后,再通过与阈值比较实现OFDM信号的帧检测。相较于混合能量检测算法,所提算法计算预设参数少,复杂度低。仿真结果表明,所提算法在加性高斯白噪声信道和多径衰落信道下带内信噪比分别取-6 dB和3 dB时即可实现零漏报率,且零漏报率的阈值选取范围比混合能量检测算法扩大了约6 dB。展开更多
基金Supported by the Educational Science Research Project of Hubei Province(B2014243)
文摘Traditional orthogonal frequency division multiplexing(OFDM) transmitter is implemented by exploiting inverse fast Fourier transform(IFFT), up-sampling, and low pass shaping filter(LPSF) modules, which occupy a large number of hardware resources and severely lower down the operation speed. To address these limitations, we propose a novel OFDM transmitter architecture, by which the aforementioned modules can be discarded and replaced with some simple switches. In the proposed architecture, direct digital synthesis(DDS) method is employed to generate digital sub-carriers and to transform OFDM data from frequency domain to time domain. Through some sophisticated simplifications, the proposed architecture can avoid using multipliers and remarkably save hardware resources. Finally, comparative experiments are carried out on field programmable gate array(FPGA) platform which demonstrates that our DDS-based architecture saves more than half of the hardware resources and doubles the achievable maximum frequency compared with traditional structure.
文摘This paper proposed an optimized fast handoff scheme for real time applications in next generation IP based CDMA wireless networks. The idea is to utilize optimized IP multicasting handoff (based on PIM SM), which is triggered by CDMA layer 2 functionality. An IP based cellular network model with WCDMA FDD air interface and IP based packet traffic is adopted. No special network entities and signaling for handoff are added in our network model. The simulation results show that low delay and low packet lost rate can be obtained.
